Printed circuit timer with arcpreventing auxiliary contacts



June 15, 1965 W. HOLZER PRINTED CIRCUIT TIMER WITH ARC-PREVENTING AUXILIARY CONTACTS Filed May 1, 1961 Fig.1.

tr y //v VEN TOR WALTER HOLZER A ttorneys United States Patent 3,189,697 PRINTED CIRCUIT TIMER WITH ARC- PREVENTING AUXILIARY CONTACTS Walter Holzer, Schutzenrain, Meersburg (Bodensee), Germany Filed May 1, 1961, Ser. No. 106,648 Claims priority, application Germany, May 10, 1969, H 39,384 2 Claims. (Cl. 200-23) This invention relates to electric control apparatus. The invention has for its object to provide a control apparatus that employs a so-called printed circuit member; the invention can be used with particular advantage in a control apparatus for a fullyautomatic washing machine.

A printed circuit comprises a panel of insulating material on which is supported a pattern of thin metallic conductors, usually in the form of metal foil. It is possible to use conductors of this kind in conjunction with a moving contact member, as the contact of a switch but the difiiculty then arises that where a circuit is made or broken arcing may occur to an extent that causes damage to the conductor, and may result ultimately in the destruction of the conductor. The problem is more acute when the circuit is frequently made and broken, and with heavier currents; in these circumstances even if the conductors are not excessively damaged, tracking may occur between adjacent conductors.

The present invention has for its object to reduce or minimize these disadvantages, so that the life of the printed circuit member is prolonged.

In an apparatus in accordance with the invention further, separate and relatively heavy-duty con-tacts are provided, and means arranged whereby such further contacts are associated with the printed circuit contacts when contact would be made or broken by the latter. Any arcing that takes place is thenborne by the further contacts.

Broadly, therefore, the invention consists of an electric control apparatus, comprising a printed circuit memher and a moving contact cooperating with a plurality of contacts provided in said member, and relatively heavy duty auxiliary contacts operated in timed relationship with the moving contact, and arranged in parallel with the contacts on said member at times when circuit is being established or broken between them.

In a preferred form of the invention, a rotary wiper contact is used, engaging suitably disposed contacts on the printed circuit panel, and the wiper contact is driven synchronously with the said further contacts.

A series of cams are provided, each operating one set of the auxiliary contacts, the cams being carried on a common carrier or on a series of carriers, such as discs; the carrier or carriers are driven by the same means as the wiper contact. Cams for this purpose can be connected readily, by inexpensive means, to the shaft of the wiper contact, with step-up or step-down speed change mechanism if desired. By this means, damage to the ends of the contacts on the printed circuit due to arcing and similar current effects is reduced. Advantageously one set of the auxiliary contacts is associated with each switching conductor of the printed circuit and arranged so that these contacts are open when contact is established between the wiper contact and the corresponding conductor of the printed circuit, and are closed when contact is being made or broken at the latter contacts, at one or other of the ends of the printed circuit contact.

Other features and advantages of the invention will appear from the following description of one embodiment thereof, given by way of example, in conjunction with the accompanying drawings, in which:

FIGURE 1 is a circuit diagram of a program selection device, suitable for a fully automatic Washing 3,189,697 Patented June 15, 1965 machine, and affording the facility of rapid pre-selection and FIGURE 2 is a development of the auxiliary contacts placed in relation to the operating times of the printed circuit contacts likewise shown as development.

Referring to FIGURE 1, a printed circuit member comprises a panel 1 of thin insulating material, on which are formed a series of conductive arcuate members 2, 3, 4, 5, 6, 7. A further inner, annular, concentric conductor 8 is also provided, and the panel carries terminal members 11, 12, 15, 14, 13 and 9 connected respectively to contacts 2 to 7 by printed connectors formed also on the panel. The conductors 2 to 7 correspond to the individual functions in the program of operation of the washing machine. It will be understood that there may be as many contacts, similar to contacts 2 to 7, as may be re quired and these can be of any suitable design. Moving over the contacts is a Wiper contact 16, which makes bridging action between the contacts such as 2 to 7 with the adjacent part of the concentric contact 8.

Wiper contact 16 is driven from a suitable driving motor by means of a shaft 17 on which the contact is mounted; there may be incorporated in this drive any suitable speed increasing or reduction gearing as required. It is convenient also that shaft 17 operate, other contacts, not shown, cam switches, snap action switches or other contacts for effecting the individual program operations.

Driving motor 18 also operates a cam disc 19 having a cut-away portion 20; a spring contact 21 bears against the periphery of the disc, and operates a moving contact 23 in relation to a stationary contact 22. The cam switch thus provided acts as a homing device for the motor, the contacts 22 and 23 being included in the energising circuit for the motor between supply terminals 30 and 31 so that the motor will continue to run until contacts 22, 23 are interrupted.

A serie of push buttons 24, 25, 26, 27, 28, 29 are provided pertaining one to each of the contacts 2 to 7; for simplicity, the circuit pertaining only to contact 4, and including push button 24, is shown. When the push button 24 is operated, the circuit for the motor 18 is completed over contacts 24 and contacts 33 of a relay 32, the relay 32 being included in the common return from all the push buttons 24 to 29. While push button 24 is depressed the motor is energised and the cam disc 19 is rotated. The circuit of the motor is thereby maintained over contacts 22 and 23. Rotation of the motor 18 causes the wiper contact to move, until it bridges contacts 4 and 8. At this point, the circuit of relay 32 is completed over a path from terminal 3%, terminal 10, contact 8, wiper 16, contact 4, terminal 15, relay winding 32 to terminal 31. Relay 32 operate and opens contacts 33, S0 that the motor will run until contacts 22, 23 are interrupted at the homing position of motor 18. Upon interruption of contacts 22 and 23, rectifier 34 operate to supply current to the armature winding of the motor 18, so that the motor stops immediately; this ensures that the wiping contact 16 will be exactly in the required position, even if push button 24 remains depressed.

As thus far described, arcing would occur between the wiping contact 16 and the ends of the contacts such as 2 to 7. To prevent this arcing, a series of cam discs 35, 36, 37, 38, 39, 40 are mounted on a common shaft and driven from motor 18. Each cam disc has a cam projection and the cam projections of the different discs are suitably phased. Cooperating with the cam discs and operated by the cam projections are a eries of auxiliary contact sets 41, 42, 43, 44, 45, 46 and 47. One contact of each set is common to the terminal 30, whilst the other contact of each set is connected to terminal members 10, 9, 15, 14, 1?, 12 and 11 through push buttons 24 through 29 to relay 32 to terminal 31.

FIGURE 2 shows the relative times of operation of the auxiliary contacts 41 to 47, in relation to the operation of the contacts 2 to '7 effected by the wiping contact 16 and the concentric ring contact 8. The wiping contact move in the direction indicated by arrow 48; it will be seen that connection is first established by the auxiliary contacts 47, and thereafter contact 16 makes connection between contact 2 and contact 8. This continues until wiping contact 16 is at a position intermediate the ends of contact 2, whereupon the auxiliary contacts 47 open. Before the wiping contact 16 leaves contact 2, auxiliary contacts 46 close and remain closed while connection is broken between 16 and contact 2. This operation is repeated for each of the succeeding contacts 3 to 7 and in this way it always occurs that there is no potential ditference existing between any one of the contacts 2 to 7 and the cooperating contact 16 when circuit is made or broken between them. 7

The life of the printed circuit member is thus extended, and the effect of the current carried by the conductors of the member is limited to the slight heating effect of the current. Accordingly, the principal factor controlling the life of the printed circuit member is that of mechanical wear and tear due to the wiping action of contact 16.

The auxiliary contacts can be closed by means other than the cam system shown in FIGURE 1. For example,

a single cam disc can be provided, around which the various auxiliary contact sets are disposed, the auxiliary contacts being then opened and closed in turn by the cam, the arrangement being such that, as before, the auxiliary contacts are related to the disposition of the contacts 2 to '7. The contacts 2 to '7 are accordingly protected against the effects of arcing in the manner described above. With the arrangements described, increasing contact resistance in the auxiliary contacts is not important in relation to the timing of the program, since the switching operation is effected at the times indicated at 49, 50, 51, 52, 53, 54 shown in FIGURE 2. The auxiliary contacts thus provide a means of adjusting the switching times very accurately. The invention can be. applied generally to electric control apparatus in which printed circuit contacts are used, but is of particular advantage for use with printed circuit switching devices for fully automatic washing machines. In this application the use of the invention enables relays or contactors to be disposed with, switching operations being performed directly by means of the printed circuit member.

I claim:

1. A control apparatus for a completely automatic washing machine comprising a printed circuit member having a plurality of contacts, a contact member, means moving said contact member so as to slide over said plurality of contacts, pairs of heavy duty auxiliary contacts connected in parallel with said contacts on said printed circuit member, separate cam means operating each of said pairs of auxiliary contacts in accurately timed relationship with the moving contact member, said cam means operating to close each pair of auxiliary contacts immediately before the moving contact memberslides upon the corresponding contact on the printed circuit memher and is opened while said moving contact member is intermediate the ends of said corresponding contact, and the next pair of auxiliary contacts is closed immediately before the moving contact member slides off said corresponding contact.

2. The invention as defined in claim 1, wherein said means moving said contact member comprises a common motor driving in accurately timed relation both the moving contact member and each of said cam means for operating said heavy duty contacts, said contacts on said printed circuit member comprising spaced arcuate segments and said moving contact member being pivotally supported in the center of said segments, said moving contact member rotating and therefore sliding over said segments, thus precisely timing the switching on and off of current through said heavy duty auxiliary contacts, whereby arcing on said printed circuit member is avoided.

References Cited by the Examiner UNITED STATES PATENTS 2,073,579 3/37 Hill. 2,656,424 10/53 Frerer et al. 200-27 X 2,995,143 8/61 Strathearn et al. 200-11 3,031,541 4/62 Holfmann 200-11 FOREIGN PATENTS 609,374 9/48 Great Britain.

BERNARD A. GILHEANY, Primary Examir zer,

MAX L. LEVY, Examiner, 

1. A CONTROL APPARATUS FOR A COMPLETELY AUTOMATIC WASHING MACHINE COMPRISING A PRINTED CIRCUIT MEMBER HAVING A PLURALITY OF CONTACTS, A CONTACT MEMBER, MEANS MOVING SAID CONTACT MEMBER SO AS TO SLIDE OVER SAID PLURALITY OF CONTACTS, PAIRS OF HEAVY DUTY AUXILIARY CONTACTS CONNECTED IN PARALLEL WITH SAID CONTACTS ON SAID PRINTED CIRCUIT MEMBER, SEPARATE CAM MEANS OPERATING EACH OF SAID PAIRS OF AUXILIARY CONTACTS IN ACCURATELY TIMED RELATIONSHIP WITH THE MOVING CONTACT MEMBER, SAID CAM MEANS OPERATING TO CLOSE EACH PAIR OF AUXILIARY CONTACTS 